[LLVMbugs] [Bug 11345] New: debug info generated for functions that are not emitted

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=11345

             Bug #: 11345
           Summary: debug info generated for functions that are not
                    emitted
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: LLVM Codegen
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: nlewycky at google.com
                CC: echristo at gmail.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Consider this testcase:

  class locale {
  private:
    void _M_add_reference() const throw() {
    }
  };
  class ios_base {
    locale _M_ios_locale;
  public:
    class Init {
    };
  };
  static ios_base::Init __ioinit;

When built without debug info, GCC and clang agree, the resulting assembly is:
        .local  _ZL8__ioinit
        .comm   _ZL8__ioinit,1,1

but where things get exciting is the debug info. Besides the
filename/directory/compiler identifier, the strings that GCC emits are

.LASF4:
        .string "Init"
.LASF5:
        .string "__ioinit"

which makes sense, there's one object named __ioinit of type Init (technically
"ios_base::Init", so emitting that would be fine too). Clang emits:

.Lstring3:
        .ascii   "__ioinit"
        .zero   1
.Lstring4:
        .ascii   "_ZL8__ioinit"
        .zero   1
.Lstring5:
        .ascii   "Init"
        .zero   1
.Lstring6:
        .ascii   "_M_ios_locale"
        .zero   1
.Lstring7:
        .ascii   "_ZNK6locale16_M_add_referenceEv"
        .zero   1
.Lstring8:
        .ascii   "_M_add_reference"
        .zero   1
.Lstring9:
        .ascii   "locale"
        .zero   1
.Lstring10:
        .ascii   "ios_base"
        .zero   1

Yow! We never emitted code for any of those functions at the very least. My
estimate is that this is causing about 60% of the extra strings. (Only an
estimate because there are other sources of differences, such as clang emitting
all case names for a given enum, while gcc only emits the used ones. I consider
clang's behaviour better.)

-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.